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To follow along with this chapter, ensure that you have:

• Unreal Engine 5.4 or later installed on your system
• A PC capable of running Unreal Engine 5 with a recommended GPU supporting hardware ray tracing
• Basic knowledge of Unreal Engine’s user interface and lighting tools
• Optional: A project with pre-built assets for testing and practice (or start with Unreal’s sample projects)

  Important note

  This book uses several different Fab marketplace assets to show examples. While not required, it is recommended to have pre-built scenes of your choice to follow along or have one you have built yourself previously.

Lumen is Unreal Engine 5’s state-of-the-art solution for dynamic global illumination (GI). Unlike traditional baked lighting techniques that require precalculations and often require significant time investments and computer power for baking, and lack adaptability, Lumen provides real-time feedback and dynamically calculates how light interacts with surfaces and environments. This makes it a revolutionary tool for artists and developers who need immediate visual accuracy without sacrificing creative flexibility.

Lumen achieves this realism by simulating the complex interplay of light rays as they bounce, scatter, and diffuse across surfaces. This technique brings lifelike realism to environments, where changes in lighting conditions, such as moving a light source or altering geometry, are instantly reflected throughout the scene.

Benefits of Lumen over baked lighting methods

Baked lighting has long been...

To unlock Lumen’s full potential, it’s crucial to properly set up your project. This section provides a step-by-step guide to enabling Lumen, optimizing performance, and avoiding common pitfalls. Remember to check the Technical requirements section at the start of this chapter before you begin, and make sure you have the minimum specs required to run UE5 as shown here: https://dev.epicgames.com/documentation/en-us/unreal-engine/hardware-and-software-specifications-for-unreal-engine.

Enabling Lumen in Project Settings

Before you can start using Lumen’s powerful dynamic lighting and reflections, you’ll need to make sure it’s turned on in your project. Don’t worry—it only takes a minute. Here’s how to enable Lumen in Project Settings.

1. Open Project Settings:
   1. Navigate to the Edit menu and select Project Settings….

   

   Figure 1.3: Project Settings...

Lighting interiors effectively is a critical skill in Unreal Engine 5, as it requires balancing realism and visual appeal. Lumen is great for creating dynamic and immersive indoor environments by simulating natural and artificial light interactions in real time. This section will guide you through techniques to achieve lifelike interiors with Lumen while maintaining performance and artistic control.

Balancing natural and artificial light sources

Indoor spaces often rely on a blend of natural light, such as sunlight filtering through windows, and artificial sources such as lamps or overhead fixtures. Lumen enables the seamless blending of these light types (See the Examples subsection):

• Natural light setup: Use directional lights to simulate sunlight, positioning them to mimic real-world angles based on the time of day. Adjust the intensity and color temperature for a soft morning glow or a warmer evening ambiance. Ensure that...

Designing breathtaking outdoor environments requires mastery of natural light and atmospheric effects. Lumen provides dynamic lighting capabilities that enable you to craft realistic, immersive outdoor scenes that respond to changing conditions. This section dives into advanced techniques for outdoor lighting using Lumen and its supporting features.

Harnessing directional light for natural sunlight and shadows

Directional light serves as the backbone of outdoor lighting in Unreal Engine. With Lumen, its interaction with the environment becomes dynamically adaptive, ensuring stunning visuals:

• Simulating natural sunlight: Adjust the intensity and color temperature of the directional light to represent different times of day. For example, use a warmer tone for sunrise or sunset and a cooler tone for midday.

Unreal Engine 5’s Lumen delivers unparalleled realism and creative control by game engine standards, but combining it with traditional lighting techniques can elevate your scenes even further. This section focuses on layering additional lighting methods with Lumen to create more refined, cinematic, and visually striking environments.

Layering traditional lighting methods with Lumen

While Lumen handles GI dynamically, traditional lights such as spotlights, point lights, and area lights enable precise control over focal points and shadow diffusion:

• Spotlights and point lights for focal highlights: Use these lights to emphasize specific areas or objects in your scene, adding drama and guiding the viewer’s attention.

For example, in a gallery setting, a spotlight can highlight an artifact, while a point light adds a subtle glow to nearby objects for ambiance.

• Area (Rect) lights for realistic...

Lumen’s dynamic GI delivers impressive results, but balancing performance and quality is essential, especially for projects targeting a wide range of hardware. This section explores strategies to profile, tweak, and optimize Lumen’s performance for smooth gameplay while maintaining visuals.

Profiling Lumen performance

Before optimizing, it’s critical to identify bottlenecks in your project. Unreal Engine provides robust profiling tools to assess Lumen’s impact on performance:

• GPU profiling with the ProfileGPU command: Use GPU profiling (ProfileGPU in console command) to view the time spent rendering each component, including Lumen’s contributions. Look for areas where Lumen’s cost spikes, such as scenes with complex geometry or numerous light interactions.

Figure 1.18: Console command location at the bottom of the Editor screen

To fully appreciate the versatility of Lumen, we’ll explore two simple real-world applications: a moody dungeon scene and a vibrant outdoor market.

Case study 1: Creating a moody dungeon scene

Atmospheric interiors such as dungeons are perfect settings to showcase Lumen’s GI and shadowing:

1. Setting up flickering torches with emissive light:
   1. Place torches strategically along the walls, using emissive materials for realistic flame glows.
   2. Add dynamic point lights near each torch to simulate the flickering effect. Adjust the light intensity and color slightly over time for authenticity.
   3. Enable Lumen’s GI to capture subtle light bounces off stone walls.

Here is an example:

Figure 1.23: No lights vs. point lights added to dungeon scene (asset source: Multistory Dungeons by Mana Station | fab.com)

2. Adding volumetric fog for eerie depth:
   ...

While Lumen is a powerful lighting solution, it is not without its challenges. Developers may encounter visual artifacts or performance limitations, particularly in complex scenes. In this section, we’ll identify some common issues and provide actionable solutions to help you maintain high-quality visuals and optimize your workflow.

Common issues with Lumen

Here are a few common issues with Lumen, along with their causes and solutions to overcome them:

• Artifacts in light, reflections, and shadows:
  • Issue: Reflections and GI may appear noisy or distorted, especially on glossy or reflective surfaces, while shadows might flicker or lack definition.
  • Cause: These issues often stem from insufficient screen-space data or incorrect light settings.
  • Solutions:
    • Adjust Reflection Method under the Lumen settings to prioritize Hardware Ray Tracing (if supported by your system) for higher-quality reflections...

In this chapter, we delved into the power of Unreal Engine 5’s Lumen system and explored advanced lighting techniques to enhance your projects. By now, you should have a deeper understanding of how to effectively utilize Lumen in various scenarios, optimize its performance, and troubleshoot common issues.

Here’s a list of the key takeaways:

• Streamlining workflow efficiency: Lumen eliminates time-consuming light baking, enabling rapid iteration and seamless integration into interactive and cinematic projects

Figure 1.28: Traditional light baking versus Lumen-enabled workflows

• Realistic lighting across scenarios: Techniques for balancing natural and artificial light sources indoors and achieving stunning realism in outdoor environments through directional lights, volumetric fog, and dynamic weather systems.
• Advanced techniques for lighting enhancement: Combining Lumen with traditional lighting methods and volumetric...

• Lighting, Exposure, and Contrast: Explore advanced techniques for achieving realistic exposure and contrast in your lighting setups. Read more here: https://www.artstation.com/blogs/shinsoj/p0Vv/lighting-exposure-and-contrast
• Daylight: Dive into the science and principles of daylight to better understand its impact on lighting design. Read more here: https://www.velux.com/what-we-do/research-and-knowledge/deic-basic-book/daylight/daylight-calculations-and-measurements

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